Here is a quote from Jean Georges Vongericten in an interview that he had with a Wall Street Journal Reporter,22 January 2011.
"The most overrated ingredient is truffle oil. It's like gasoline. I never use it in my restaurants. It's heavy, and it repeats on me."
I sometimes have a dish at my fav local place that uses truffle oil on it; but I have to say it is not a key ingredient, for my tastes.